The Prime Minister’s recent announcement that Parliament would be prorogued, thereby severely curtailing the opportunity for parliamentary debate, raises important issues of constitutional principle and law, and also issues concerning fact and causation. They are examined in turn.

Constitutional Principle and Law

We begin with constitutional principle and law. We seek to decide whether the courts should intervene via judicial review, in order to prevent Parliament from being prorogued. We do not, however, begin with a clean slate. We look to case law where the courts have intervened to curtail prerogative power, discern the underlying principles, and then decide whether those are applicable to the case at hand.

Consider then the principal case law concerning constraints on prerogative power dating back to the seventeenth century. The constraints on prerogative power embodied in Proclamations, De Keyser and Miller all protect parliamentary sovereignty. Parliament is the legitimate legislator within the UK and the case law protects that authority from being undermined. If the executive could change the law of its own volition, it could thereby bypass legislation without amendment or repeal, hence the principle in Proclamations. If the executive could use the prerogative where Parliament had already addressed the issue in an existing statute it could then avoid the legislation crafted by Parliament, hence the principle in De Keyser, and its extension to cases where the prerogative would frustrate the legislation. If the executive could render a constitutional statute devoid of effect through recourse to the prerogative, the statute would not be worthy of that appellation, hence the reasoning on this issue in Miller, drawing on that in HS2.

Proclamations protects parliamentary sovereignty directly, by preventing recourse to the prerogative where it would change the law. De Keyser and Miller protect sovereignty indirectly: the former by precluding use of the prerogative where the formal law is left intact, but the executive seeks to circumvent it by use of the prerogative; the latter case by preventing a constitutional statute from being emasculated through executive action, even if it remained formally on the statute book.

The salient issue in relation to prorogation is whether the Prime Minister’s discretionary power should be limited pursuant to the principles underlying the case law set out above. The argument for an affirmative answer is compelling. This is so for two related reasons.

First, to contend that there is some difference between the existing case law and the present situation does not withstand normative examination. The reality is to the contrary, the rationale for intervention to protect parliamentary sovereignty is even stronger than in the preceding cases. Consider the following two propositions. Parliament has enacted a statute, the executive seeks to circumvent it by recourse to the prerogative, and the court intervenes to protect parliamentary sovereignty via the De Keyser principle. Parliament wishes to exercise its legitimate authority through enactment of a statute, or in some other way, the executive precludes this through prorogation, and the court is said to be powerless to intervene.

This distinction makes no principled sense, more especially because the latter abuse of discretionary power is more far-reaching and significant than the former. The former impacts only on a particular statute. The latter constitutes a pre-emptive strike that takes Parliament out of the entire game for the crucial period during which it is prorogued. It affects not merely one piece of legislation, but its capacity to exercise the totality of its legislative authority, thereby severely curtailing the opportunity for parliamentary voice on an issue that, whatsoever one’s views about Brexit, is of major importance for the UK’s future. This is, moreover, the reason why judicial intervention in this instance would not signal some general judicial intrusion in this terrain. The use of prorogation in this instance is singular, and warrants judicial intervention.

Secondly, the case for judicial intervention is also compelling because of the impact of the abuse of power in relation to prorogation on the sovereignty principle itself. The sovereignty of Parliament is the foundational principle underlying the unwritten UK constitution. This sovereignty resides with Parliament, not with the executive. Compare once again the preceding scenarios, and their relative impact on this foundational principle. The De Keyser scenario represents a challenge to sovereignty, since the executive seeks to bypass an existing statute, through recourse to the prerogative. It was for this very reason that the House of Lords intervened to prevent this. The prorogation scenario is more far-reaching in its impact on sovereignty. The reason is not hard to divine. The political discussion of prorogation by the present government was predicated on the assumption that it could be legitimate for the Prime Minister to make use of this power intentionally to bypass what was felt to be a recalcitrant Parliament. This is not and cannot be constitutionally correct. To subscribe to such reasoning per se diminishes parliamentary sovereignty as a foundational principle, and transforms the UK constitutional order such that the cards become stacked in the executive’s favour.

Nor can such reasoning be defended on the ground that the Prime Minister believes that this use of prorogation would be justified in order to fulfil the will of the people. Let us leave aside the fact that the Prime Minister presently has the slender legitimacy that comes from a vote of 92,000 Conservative members; let us leave aside also the fact the divination of the will of the people in terms of being content with a no-deal Brexit is fraught with difficulty. The root problem with this reasoning is more serious, and betrays a deeper lack of understanding of our constitutional order. The sovereignty principle inheres in Parliament and the totality of members thereof at any one point in time. The very idea that Parliament can be swept aside because its view does not cohere with the executive is to stand principle on its head. We are constitutionally impoverished if we regard this as the new constitutional norm.

Fact and Causation

There is no doubt that supporters of prorogation will attempt to blunt the preceding argument by repeating the claim that it was not driven by the desire to forestall discussion of Brexit, but because the Prime Minister wished to press ahead with his new agenda, and did not wish to wait until after the presently existing Brexit deadline. This is then coupled with the argument that the present parliamentary session has been very long, and that it is legitimate to signal the new beginning with the Queen’s speech scheduled for mid-October.

A response to this argument, voiced by many in the aftermath of the prorogation announcement, is simply to regard it as a veneer that conceals the real reason for the prorogation, which is to limit the time for parliamentary voice on Brexit. Truth to tell, there have been government statements post the prorogation announcement that acknowledge its impact on the domestic Brexit agenda, and that in Brussels.

A second response would be that, even if we assume that the desire to press ahead with a new agenda represented reality, the costs in terms of the impact on parliamentary sovereignty are simply far too great, more especially at this crucial time for Brexit deliberations. Indeed, one could press further in this regard: given that the present parliamentary session has lasted a long time, a few more weeks would hardly make a crucial difference in terms of getting the Prime Minister’s new agenda on the road.

The third response is that the preceding argument makes no sense in its own terms. Consider the following. We have a fact, the Prime Minister’s statement that he wishes to press ahead with his new agenda. We have assertion of a second fact, prorogation is said to be necessary to enable the first fact to happen. There is assumed to be causation between the two. This assumption is a non-sequitur. If the Prime Minister wishes to kick start his new agenda now, there is nothing legally or politically to prevent him from instructing civil servants in the relevant departments from pressing on to draft the requisite legislation, sort out the finances and the like. They were probably already doing this before prorogation. The reality is not merely that the causation is lacking. It is that prorogation will almost certainly hamper prime ministerial efforts to roll out the new agenda. If prorogation occurs, Parliament does not sit, no legislation is enacted, and there is a danger that some necessary Brexit legislation will be lost or impeded because of prorogation. If Brexit happens there will then be a log-jam of Brexit-related measures that require enactment, thereby pushing into the long grass efforts legislation designed to address non-Brexit issues.